Linkage and recombination

Genetic Linkage

The tendency of genes that are located close together on a chromosome to be inherited together.

Recombination Frequency (RF)

The ratio of recombinant offspring to the total number of offspring, used to estimate genetic distance between loci.

Parental Gametes

Gametes that have the same allele combination as the parents, resulting from no crossing over.

Recombinant Gametes

Gametes that have a different allele combination than the parents, resulting from crossing over.

Coupling Configuration

Configuration where dominant alleles of linked genes are located on the same chromosome, e.g., AB/ab.

Repulsion Configuration

Configuration where dominant alleles of linked genes are located on different homologs, e.g., Ab/aB.

Crossing Over

The process during meiosis where non-sister chromatids exchange genetic material, leading to recombinant gametes.

Testcross

A breeding experiment between a homozygous recessive individual and an individual with an unknown genotype, used to determine the genotype.

Phenotypic Ratio

The relative frequency of different phenotypes resulting from a genetic cross.

Maximum Recombination Frequency

The upper limit of recombinant gametes produced, which is 50%, indicating genes are either on separate chromosomes or far apart on the same chromosome.

Dihybrid Cross

A cross between two organisms that are heterozygous for two traits.

Centimorgan (cM)

A unit of measure for genetic linkage, where 1 cM equals a 1% chance of recombination between two loci.

Mapping Unit (m.u.)

Equivalent to a centimorgan (cM), used to express genetic distances between loci.

Nonrecombinant Progeny

Offspring that inherit the same combination of alleles as their parents.

Recombinant Progeny

Offspring that inherit a new combination of alleles due to crossing over.